Desktop rapid prototyping

Cuts costs and improves designs

Producing real physical models directly from 3D CAD models is possible
through an increasingly automatic process called rapid prototyping. Rapid
prototyping is very useful to those who design in 3D because it helps
identify the need for significant changes earlier in the product development
cycle. This in turn reduces cost and improves performance. If you still
primarily use 2D designs, rapid prototyping is yet another reason to switch
to 3D.

Figure 1. Not quite
small enough to sit on your desk, this officefriendly rapid prototyping
system, Z Corp.'s Z406, is roughly the size of an office copier.

The diverse areas in which rapid prototyping is used continues to grow
and astound even long-time users. Examples include engine part mold masters,
architectural scale models, medical implants, and even final products,
such as the Invisalign orthodontic retainers. The adoption rate of rapid
prototyping among engineers and designers follows closely that of 3D CAD
use, although rapid prototyping is at a much earlier stage of popularity
and time in the market.

In this article, we address a subsection of the rapid prototyping field
that is generally less expensive ($7,500–$190,000) and more convenient
for designers to use directly. This subset, known as office-friendly or
desktop prototyping, is gaining popularity thanks to its use of more environmentally
friendly materials and a significant reduction in physical machine size.

Most of the machines we found are larger than your average printer, more
similar in size to a copying machine—still quite an office-friendly
size (figure 1). For a broader perspective on rapid prototyping technology,
please see our previous article in the May
2001 issue of Cadalyst as well as the Wohlers
Report 2002.

This prototype is a full-size
turbo charger housing that was built in 5 hours, 41 minutes, plus
30 minutes of finishing time, using a Z Corp. system. A monochrome
version took 3 hours, 11 minutes to create. The model measures 8"
x 6" x 5" and occupies 38 cubic inches. Material cost for
the color prototype was $97.14, and $65.60 for the monochrome version.

Office-friendly 3D printers
Traditionally, rapid prototyping machines needed their own lab-type area
because their operational characteristics (noise, fumes, possible contamination
of resin, residue, UV-sensitive materials, and so forth) were not appropriate
for the office. Labs provided extra electrical power, space for machines
the size of industrial refrigerators, a separate area for noxious build
materials, venting ducts for outgassing, and noise insulation from the
office. Users also needed a fair amount of training to operate these machines
properly.

Figure 2. In this example, reverse-engineering
data was used to make a detailed 2D drawing.

Figure 3. This 3D CAD model, created from
the 2D drawing, was sent to the rapid prototyping system.

Figure 3. This 3D CAD model, created from
the 2D drawing, was sent to the rapid prototyping system.

Figure 5. The finished machine casting.

A goal of the rapid prototyping industry is to make a class of rapid
prototyping machines that are as officefriendly as laser printers. Such
units must be smaller and more movable than traditional systems, with
no special venting or power requirements. User training should be minimal.
The first generation of 3D printers with these characteristics is now
available. A typical air-conditioned office is the assumed setting for
these devices. Though some machines approach the size of a laser printer,
it's still too soon to call them desktop rapid prototypers.

Delivering an office-friendly rapid prototyping system is more complicated
than a paper printer because the user's final output requirements vary
considerably. Rapid prototyping vendor 3D Systems divides the final outputs
desired into five categories:

concept models

prototypes

patterns

tools

finished parts

Concept models, prototypes, and patterns are a strong suit of 3D printers,
and some machines provide green parts that can assist in the rapid manufacturing
realm. The relationship between price and functionality is not as clear
as it used to be. Even so, the less-expensive office machines have not
eclipsed their more expensive forebears.

Product development engineer Jim Pike at the Sturm division of the Sulzer
pump company provided a real-world example of rapid manufacturing via
rapid prototyping for a replacement impeller part (see figures 2–5,
above). prototyping

This feature surveys the office-friendly offerings of four manufacturers
of rapid prototyping systems. In addition, the box below shows some tabletop
milling machines that can quickly produce metal parts and models.

Benchtop milling machines serve rapid prototyping roles

The MDX-650
(shown at right) and MDX-500 (not shown) benchtop milling machines
from Roland DGA (www.rolanddga. com) quickly turn CAD files
into 3D prototypes and molds. Powered by AC servo motors on
all three axes, they mill ABS, modeling wax, aluminum, brass,
and other nonferrous metals. With its optional rotary axis,
the MDX-650 mills the full circumference of objects. Both mill
as much as 200 per minute with no finishing required. The MDX-650
has a maximum work area of 25.56" x 17.69" x 6.06",
and the MDX-500 has a maximum work area of 19.63" x 12.94"
x 4.125".

The Roland MDX-15 (not
shown) and MDX-20 (shown at left) desktop milling machines are
ideal for jewelers and product designers working on a budget.
They mill chemical wood, resin, aluminum, and brass and incorporate
RAPS technology to scan with resolution up to 0.002". Maximum
work area is 8" x 6" for the MDX-15 and 6" x
4" for the MDX-20. Both have a z-axis height of 2.38".

3D systems
The company that started the rapid prototyping industry maintains a reputation
for producing machines that generate accurate and functional parts.

3D Systems recently announced a new product called the InVision 3D Printer
(figure 6) for the office-friendly rapid prototyping market segment. The
InVision 3D Printer uses a new model material and support material (figure
7). The model material is a translucent, durable acrylic photopolymer
blend appropriate for durable communication models and assembly analysis
prototypes. The support material is a wax-based blend.

Part sizes appear to be in the same range as those produced by other
midpriced rapid prototyping systems (see comparison
table).

3D Systems' ThermoJet printer remains as a solution for investment casting
and communication models. The ThermoJet provides less durable models but
supports colors. InVision is available through the company's worldwide
direct sales force and its network of channel partners, resellers, and
distributors.

Solidscape
Solidscape positions its 3D printers as highly accurate machines that
exceed concept model requirements to produce precise models and patterns.
Models are accurate to one-thousandth of an inch per inch in the x-, y-
and zdimensions. This enables an excellent surface finish with very fine
feature detail. Little or no postprocessing is required. This precision
comes at the expense of speed and potential part volume.

Two types of proprietary materials are available, and both are nontoxic.
Support structures for the materials dissolve easily. The build material
has a fast melt-out in casting and negligible thermal expansion. It leaves
no ash or residue. The company estimates that at an 85% duty cycle, a
typical user spends $200–$250 per month on materials.

Solidscape systems can run unattended for 72 hours. They have a small
footprint and are about 5 tall. The only requirements are that the unit
be in an air-conditioned room with standard power outlets.

Solidscape user Norm DePeau of Sturm, Ruger is very positive about his
machine's contribution to rapid manufacturing: "This capability is
invaluable as a complement to the investment casting process. Many customers
are not prepared to invest in wax die tooling during the new product development
phase. The Solidscape Pattern Master allows our casting operations to
introduce customers to the use of castings with a significantly lower
entry cost. The Pattern Master produces high-precision patterns that can
be used directly in the investment casting process in place of the wax
patterns normally generated from hard tooling (figures 8 and 9). As the
project evolves and designs become firm, customers are better prepared
to fund the hard tooling needed to produce investment castings."

Figure 8. Rapid
prototyping components for firearms. The model is built from a green
material, and the red material serves as the support structure.

Figure 9. Once the supports dissolve,
you can see the intricate parts that the Solidscape Pattern Master
is capable of producing. Images courtesy of Sturm, Ruger & Co.
Inc.

Stratasys
Stratasys is an established rapid prototyping vendor that made news early
this year with the introduction of its Dimension 3D printer (figure 10).
"Stratasys just released the Dimension to quickly create usable,
functional models at the engineer's desk," said Mike Ontiveros of
CAD/CAM Systems, a Stratasys reseller. "Confidentiality is of great
concern, and the Dimension will keep intellectual property (design and
mechanical technology) in house."

Figure 10. The Dimension
printer uses two self-loading cartridges for the model and support
materials.

This machine is very office-friendly. It uses a standard 110V AC power
connection, is easy to network, and notifies you via e-mail, pager, or
the Web when it completes a part. The material cartridges plug in much
like toner cartridges —no chemicals, powders, or fumes.

With a base price of $29,900, it's currently the least expensive machine
on the market, even with the optional annual maintenance plan (10% of
price), although not by much. The Dimension is based on the proven technology
found in the larger FDM (fused deposition modeling) machines that Stratasys
makes.

The Dimension offers only one material choice, an ABS plastic with a
tensile strength of 5,000psi. This is equal to or better than some other
grades of commercially available ABS. Because of rapid prototyping build
characteristics, the parts may be weaker in the x,y plane. This material
produces very functional parts that can even be melted, if necessary,
for shape or snap-fit tweaks. A fairly detailed pagersized part we saw
took about 1.5 hours to build with a material cost of about $7.

Material cartridges contain an EPROM chip that tracks used and unused
material to confirm that the necessary material for the part volume is
available before the Dimension builds the model. You can switch cartridges
midway through part building, if necessary. You can also pause the job
to switch cartridge colors.

Dimension automatically builds breakaway supports. You must remove the
supports by hand after the part is built. Cleanup involves a minimal amount
of mess that is more office-friendly than that left by the powder used
by some systems.

The setup software for Windows is easy to use. Another program in the
machine handles status and administration of the part. Setup parameters
include:

Part orientation

Slice thickness

Part build type (solid, thin-walled, thick-walled)

Support type (dense, sparse)

Preview build paths

Finished part notification options

Stratasys sells its rapid prototyping machines through resellers in the
United States and directly abroad.

Z Corp. "The earlier in the design process you can build concept
models, the earlier you can resolve problems and issues," explained
rapid prototyping reseller Mark Kemper of EMS USA. "Companies in
the past would build concept models only near the end of the design cycle
because of the time and cost of either using an outside service bureau
or buying their own equipment. When the average part takes ten hours to
build and costs $1,000 or more, how many would you build? When a part
takes three hours to build and costs $20, you can afford to do many more
models and do them earlier in the process.

"With Z Corp.'s full 3D color capabilities," he added, "users
can analyze engineering data such as CFD, FEA, mold flow, and other analysis
results right on their model." See figures 11 and 12 (below) for
examples.

Figure 11. The cell phone analysis
was performed with Moldflow software, then molten plastic flow characteristics
were transferred to a Z Corp. rapid prototyping system via a VRML
file. Image courtesy of EMS.

Figure
12. Turbine blades were analyzed with FEA software, and the stress
colors were built into this Z Corp. rapid prototyping model. Image
courtesy of EMS.

Z Corp. earned its strong reputation as a leader in the 3D printer market.
The company claims to have the fastest 3D printers in the world with the
capability to produce a handheld part in less than an hour. They were
also the first to provide full-color models. Color information displayed
in software analysis packages is passed via VRML files to complement the
STL file used for geometry.

Z Corp. attributes its relatively low product prices to using off-the-shelf
components. These machines also have low operating costs. The company
offers three different models for $33,500, $66,500, and $175,000. The
first two are the size of an office copier and connect to computers via
a serial port.

Two types of materials are currently available (a starch-based powder
and a plaster) that enable the machines to produce concept models, prototypes,
and patterns.

You can switch materials in a 20- minute, two-step process. First, you
vacuum out the first powder, which you can reuse. Second, switch the binder
over and purge the old resin.

The only complaint we heard about the material is that the powder is
a little messy when you take it out of the machine, so you'll need a small
cleanup area.

Penetrating and sealing models with a material similar to Superglue can
result in a small amount of harmless outgassing with an odor that is not
noxious or irritating.

In the United States, Z Corp. machines are available directly from the
vendor and through resellers. Internationally, they are sold through distributors.

Service Bureaus remain important
Owners of 3D printing systems frequently report that they obtained rapid
prototyping models through service bureaus before they bought their own
systems. Many still use these outside resources to produce types of rapid
prototyping models that their in-house systems can't create. In some cases,
this may simply be due to the hassle and cost associated with switching
out one material type for another.

Todd Grimm, marketing manager for dedicated rapid prototyping service
bureau Accelerated
Technologies, noted in a recent paper that choosing the right technology
for your desired end product is difficult to do without hands-on experience.
A good service bureau guides inexperienced rapid prototyping customers
through selecting the right material and prototyping method.

"I think service bureaus will always exist because many companies
require very few parts, and even with the low prices of 3D printers, they
could never justify spending the money," explained reseller Mark
Kemper.

Figure 13. A Z Corp.
system took 6 hours, 44 minutes to produce this fullscale hydraulic
pump case that masures 8" x 10"x 7". Part volume is
43 cubic inches, and materials cost $71.87. Finishing the part required
another 45 minutes of work.

"What 3D printers have done is open a whole new market of small-
to medium-size companies that could benefit from rapid prototyping but
could never make a $100,000-plus investment in the technology. In addition,
material costs used to be $10 or more per cubic inch. Z Corp.'s 3D printers
can build parts for about $1.50 per cubic inch and do it 10 times faster
[than was previously possible]," he said (figure 13).

Some online marketplaces, such as Protomarket.com, let you request rapid
prototyping quotes from different service providers. Other sites, such
as Quickparts.com, provide quotes from a single vendor based on part files
you upload.

Rapid manufacturing with rapid prototyping
"[Rapid manufacturing] offers a lot of potential for small batches
of parts because the cost and delivery time can be very attractive,"
noted Kemper. "For example, Z Corp.'s new Z Cast Direct Metal Casting
and some new resins codeveloped with Vantico allow customers to make more
functional metal parts. Other concept modelers—3D Systems' ThermoJet,
for example— have always been good at the investment casting process.
3D Systems has also joined with DSM Somos to form a new company, OptoForm.
OptoForm will develop advanced digital manufacturing technology that will
build actual parts from composite plastic, ceramic, and metal. Such technology
will eliminate the need for hard tooling.

On the flip side, Kemper notes that "traditional methods such as
NC machining have also been moving forward. Machine tools continue to
come down in price, while high-speed machining and automated CAM systems
are more powerful than ever."

About the Author: Mark Huxley

About the Author: Steven Weisberg

Autodesk Technical Evangelist Lynn Allen guides you through a different AutoCAD feature in every edition of her popular "Circles and Lines" tutorial series. For even more AutoCAD how-to, check out Lynn's quick tips in the Cadalyst Video Gallery. Subscribe to Cadalyst's free Tips & Tools Weekly e-newsletter and we'll notify you every time a new video tip is published. All exclusively from Cadalyst!Follow Lynn on Twitter